Is there a trade‐off between aggressiveness and overwinter survival in Phytophthora infestans?

Abstract

Summary1. Selection during interepidemic stages is crucial for the evolution of pathogen populations. Trade-offs involving aggressiveness (quantitative pathogenicity) have rarely been explored in pathogens with a life cycle requiring the disease-causing organism to change organs within the same host. 2. We investigated the existence of a trade-off between aggressiveness and survival in Phytophthora infestans , the pathogen causing potato late blight. In France, P. infestans behaves as an obligate biotroph, surviving in infected tubers. Aggressive isolates, which are favoured during the epidemic, may exhaust their nutrient supply too quickly to bridge seasons, resulting in a possible trade-off between the two life stages. 3. We inoculated tubers with isolates possessing different aggressiveness levels, let them overwinter as outdoor piles at three different sites, and scored the proportion of live tubers the following spring. 4. At two sites, infection caused early tuber sprouting, which can be seen either as a manipulation of the host by the pathogen, or as an attempt by the host to escape. 5. Overwinter survival was higher for control than for inoculated tubers, but did not differ between tubers inoculated with different isolates. This suggests that aggressiveness should gradually increase in P. infestans populations, unless a trade-off occurs at another stage of the life cycle.

Seasonal Changes Drive Short-Term Selection for Fitness Traits in the Wheat Pathogen Zymoseptoria tritici

“…Directional selection for increased aggressiveness during the epidemic period was established experimentally for Phytophthora infestans, but no evidence of any trade-off between aggressiveness and overwinter survival was found (31,46). Further experimental investigations taking into account the pathogenic and saprophytic phases of the disease cycle (40,41), guided by theory (43,47), would be appropriate for characterizing the effect of seasonality on year-to-year disease transmission.…”

Life History Trade-Offs and Relaxed Selection Can Decrease Bacterial Virulence in Environmental Reservoirs

“…This ‘conflicting selection hypothesis’ is seldom directly tested but some studies support it demonstrating that virulence traits can incur fitness costs in environmental reservoirs [8], [20]–[22]. Fitness trade-off between within-host and outside-host environments has also been observed in some [23] but not all plant pathogens [24]. Instead of trading off with survival traits, virulence traits could also be neutral in the external environment.…”

Plant paleopathology and the roles of pathogens and insects

“…Once dispersed, the pathogen may overwinter or otherwise survive an inclement interval, typically in an encysted state within the primary or alternate host plant, in a medium such as the soil, or in the bodies of their insect vectors. Eventually the pathogen emerges, producing inoculum that may infect a new host plant to continue the cycle (Montarry et al, 2007). Symptoms of viral and bacterial infection can include foliar wilt, yellowing (chlorosis), browning of major veins, and splotches of necrotic tissue (Bolton et al, 2006).…”